US6254084B1

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Info

Publication number: US6254084B1
Application number: US09/377,388
Authority: US
Inventors: Andrew D. Hellmer
Original assignee: Olympus America Inc
Current assignee: Olympus America Inc
Priority date: 1999-08-19
Filing date: 1999-08-19
Publication date: 2001-07-03
Anticipated expiration: 2019-08-19

Abstract

A feed enhancer for eliminating an unevenness in height from a paper stack to be printed by a printer. The printer has a paper feeder including a paper tray for storage of the paper stack on a top surface thereof and for feeding individual paper from the paper stack into the printer for subsequent printing. The feed enhancer has an elongated strip disposed at the top surface of the paper tray and positioned perpendicular to a direction in which the individual paper is fed into the printer such that the feed enhancer evens out the unevenness in height of the paper stack in an area of the paper stack that is to be fed into the printer. Also provided are a printer and printer tray having the feed enhancer of the present invention.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The field of art to which this invention relates is-printers, in particular, a feed enhancer for a high volume printer having a top-feeder in which paper stock having labels and/or perforations are fed into the printer.

2. Description of the Related Art

In printers of the prior art, particularly those which employ a top-feeder for storing and feeding paper into the printer, paper which has a label affixed thereto or which has one or more perforations presents a problem in that it does not properly feed into the printer. Printing on such paper is particularly troublesome because the paper does not sit flatly upon a feeder tray due to the labels or perforations.

Atypical printer100 of the prior art having such a top-feeder paper feed arrangement is shown in FIGS. 1A and 1B. The top-feeder102 generally includes apaper tray103 and employs apick roller104 for contacting and feeding a sheet ofpaper106 from the top of apaper stack108 into theprinter100. A gearbox andmotor assembly110 drive the pinch roller as necessary to feed thepaper108. If the paper in thepaper stack108 does not sit flatly on thepaper tray103, thepick roller104, which is generally located in the center of the paper along a central axis C—C, does not effectively engage and feed thepaper108 into theprinter100.

Examples of types of paper which do not lie flatly on thepaper tray103, are illustrated in FIGS. 2A-2C. Respective stacks of the types of paper illustrated in FIGS. 2A-2C are illustrated in FIGS. 3A-3C together with thepaper tray103 andpick roller104 of FIG.1.

FIG. 2A illustrates a sheet ofpaper200 having alabel202 on one side. Thelabel202 adds a significant thickness to the overall thickness of the sheet ofpaper200 in the area of thelabel202. As can be seen in FIG. 3A, when stacked on apaper tray103 of aprinter100 having atop feeder102, thepaper200 has a greater height (H1) on the side with thelabel202 than the height (H2) on the side without thelabel202. Because of this uneven height (H1>H2), thepick roller104 only engages thepaper200 on a portion of its width and causes thepaper200 to rotate as it is being fed into theprinter100.

FIG. 2B illustrates a sheet ofpaper210, having twoperforations212. Theperforations212 run in the same direction as the direction that thepaper210 is fed into theprinter100. As can be seen in FIG. 3B, when stacked on apaper tray103 of aprinter100 having atop feeder102, thepaper210 has a greater height (H3) on the sides than in the middle (H4) (alternatively, if the paper stack is turned 180 degrees such that the top sheet is at the bottom, the paper stack will have a peak at each of the perforations resulting in an M-shaped stack). Because of this uneven height (H3>H4), thepick roller104 does not properly engage thepaper210 leading to improper feeding of thepaper210 into theprinter100.

FIG. 2C illustrates a sheet ofpaper220, having asingle perforation222. Theperforation222 runs in a direction perpendicular to the direction that thepaper220 is fed into theprinter100. As can be seen in FIG. 3C, when stacked on apaper tray103 of aprinter100 having atop feeder102, looking from the side of the paper stack, a portion224 of thepaper220 decreases in height from theperforation222 to the end of thepaper226. (alternatively, if the paper stack is turned 180 degrees such that the top sheet is at the bottom, the portion224 will increase in height from theperforation222 to the end of the paper226). Because of this uneven height, thepick roller104 does not properly engage thepaper210 leading to improper feeding of thepaper210 into theprinter100.

These problems ultimately cause the

paper

200,210,220 to jam in theprinter100 resulting in downtime of theprinter100 and possibly, expensive maintenance. It should be apparent to those skilled in the art, that these paper configurations are given by way of example only and not as an exhaustive listing thereof. For example the paper may have a combination of those shown or others not shown such as pre-printed stock which has a tendency to curl when stacked upon theprinter tray103.

Devices are known in the prior art for addressing the uneven thickness and shape of paper to be fed into a printer. The prior art teaches devices for compensating for variations in the thickness between individual sheets of a paper stack being fed into a printer. The prior art devices achieve their objective by sensing the thickness of each piece of paper being fed into the printer and adjusting certain parameters within the printer according to the sensed thickness.

While these devices have their advantages, they are generally complex, costly, and difficult to implement on existing printer designs.

For these reasons a feed enhancer is needed which is simple, inexpensive, easy to retrofit onto existing printers and which can compensate for paper stacks that do not lie flatly and evenly upon a printer feeder which are to be fed into a printer, particularly one which employs a top-feeder system.

SUMMARY OF THE INVENTION

Therefore, it is an object of the present invention to provide a simple feed enhancer for a printer.

It is a yet a further object of the present invention to provide an inexpensive feed enhancer for a printer.

It is still yet another object of the present invention to provide a feed enhancer which is easily retrofitted onto existing printers.

Accordingly, the present invention provides a feed enhancer disposed on a surface of a paper feeder tray to compensate for variations in height and/or shape of a paper stack placed upon the paper feeder tray caused by labels or perforations in/on the individual paper in the stack. The feed enhancer is disposed perpendicular to the direction that the paper is fed into the printer.

In a first variation of the feed enhancer of the present invention, a feed enhancer for eliminating an unevenness in height from a paper stack to be printed by a printer is provided. The printer has a paper feeder including a paper tray for storage of the paper stack on a top surface thereof and for feeding individual paper from the paper stack into the printer for subsequent printing. The feed enhancer comprises an elongated strip disposed at the top surface of the paper tray and positioned perpendicular to a direction in which the individual paper is fed into the printer such that the feed enhancer evens out the unevenness in height of the paper stack in an area of the paper stack that is to be fed into the printer.

In a second variation of the feed enhancer of the present invention, a printer tray for eliminating an unevenness in height from a paper stack to be printed by a printer is provided. The printer has a paper feeder including the paper tray for storage of the paper stack on a top surface thereof and for feeding individual paper from the paper stack into the printer for subsequent printing. The printer tray comprises a feed enhancer having a heightened portion disposed at the top surface of the paper tray and positioned perpendicular to a direction in which the individual paper is fed into the printer such that the feed enhancer evens out the unevenness in height of the paper stack in an area of the paper stack that is to be fed into the printer.

In a third variation of the feed enhancer of the present invention, a printer for eliminating an unevenness in height from a paper stack to be printed is provided. The printer has a paper feeder including a paper tray for storage of the paper stack on a top surface thereof and for feeding individual paper from the paper stack into the printer for subsequent printing. The printer comprises a feed enhancer having a heightened portion disposed at the top surface of the paper tray and positioned perpendicular to a direction in which the individual paper is fed into the printer such that the feed enhancer evens out the unevenness in height of the paper stack in an area of the paper stack that is to be fed into the printer.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of the apparatus of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings where:

FIGS. 1A and 1B are a front and side view, respectively, of a paper feeder of the prior art illustrating a stack of paper to be printed thereupon.

FIGS. 2A-2C illustrate examples of paper types which do not sit evenly on a feeder tray of the printer of FIG.1.

FIGS. 3A-3C illustrate respective paper stacks of the paper types of FIGS. 2A-2C shown sitting upon the paper tray of the printer of FIG.1.

FIG. 4 is a isometric view of the first embodiment of the feed enhancer of the present invention.

FIGS. 5A-5C illustrate the respective paper types and stacks of FIGS. 3A-3C shown with the first embodiment of the feed enhancer of the present invention.

FIG. 6 is a side view of a second embodiment of a paper tray having the feed enhancer of the present invention.

FIG. 7 is a side view of a third embodiment of a paper tray having the feed enhancer of the present invention.

FIGS. 8A and 8B are side sectional views of the feed enhancer of FIG. 7 taken alongline8—8, FIG. 8A illustrating the elongated strip at a heightened position above the top surface of the paper tray, FIG. 8B illustrating the elongated strip flush with the top surface of the paper tray.

FIGS. 9A and 9B are front sectional views of the feed enhancer of FIG. 7 taken alongline9—9, FIG. 9A illustrating the elongated strip at a heightened position above the top surface of the paper tray, FIG. 9B illustrating the elongated strip flush with the top surface of the paper tray.

FIG. 10 is a partial sectional view of the locking means of the feed enhancer of FIG. 8A taken alongline10—10.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Although this invention is applicable to numerous and various types of printers and paper, it has been found particularly useful in the environment of printers employing a top-feeder and the types of paper illustrated in FIGS. 2A-2C. Therefore, without limiting the applicability of the invention to top-feeder printers and the types of paper illustrated in FIGS. 2A-2C, the invention will be described in such environment.

Referring now in detail to FIG. 4, a first embodiment of a feed enhancer for eliminating an unevenness in height from a paper stack to be printed upon by aprinter100 is provided. The first embodiment feed enhancer is generally referred to byreference numeral400. Thefeed enhancer400 comprises anelongated strip402 which is preferably fabricated from aluminum and is preferably 1″ or less in height (h). Theelongated strip402 is preferably the same width (w) or smaller as the width of the paper being fed into theprinter100. For example, if 8½×11 inch paper is being fed into the printer with the 8½ inch side first, the feed enhancer would have a maximum width w=8½ inches and preferably not less than 6 inches wide.

Thefeed enhancer400 is disposed on atop surface103aof thepaper tray103 and positioned perpendicular to a direction in which the individual paper is fed into theprinter100 such that thefeed enhancer400 evens out the unevenness in height of the paper stack in an area of the paper stack that is to be fed into theprinter100.

Thefeed enhancer400 preferably also has a mounting means for mounting theelongated strip402 to thetop surface103aof thepaper tray103. In the typical case, thetop surface103aof thepaper tray103 is ferric and the mounting means is amagnetic strip404 fastened to theelongated strip402 whereby theelongated strip402 is mounted to thetop surface103aof thepaper tray103 by a magnetic attraction between themagnetic strip404 attached thereto and thetop surface103aof thepaper tray103. Preferably, themagnetic strip404 is fastened to theelongated strip402 with an adhesive. The feed enhancer of FIG. 4 is shown with a cut-out406 dividing themagnetic strip404 into two sections. The cut-out allows theelongated strip404 to not interfere with any raised projections or irregularities (not shown) on thetop surface103aof thepaper tray103 that may correspond to the area of the cut-out thereby permitting thefeed enhancer400 to sit flushly on thetop surface103aon thepaper tray103.

Referring now to FIGS. 5A-5C, therein are illustrated views corresponding to FIGS. 3A-3C but shown with the feed enhancer of FIG. 4 disposed on thetop surface103aof thepaper tray103 in which the unevenness in the height of the paper stacks200,210,220, respectively, is evened-out in the area of the pick roller. It should be apparent to those skilled in the art, that the

paper

200,210,220 illustrated in FIGS. 5A-5C, respectively, will feed properly into theprinter100, thereby reducing the likelihood that the paper will become jammed therein.

Referring now to FIG. 6, a second embodiment of the feed enhancer of the present invention is illustrated therein. FIG. 6 illustrates aprinter tray600 which has a heightenedportion602 disposed at the top surface of thepaper tray600 and positioned perpendicular to a direction in which the individual paper is fed into theprinter100. The heightenedportion602 preferably comprises a stepped portion integral with atop surface600aof thepaper tray600. The dimensions of the heightenedportion602 are preferably the same as discussed previously with respect to the feed enhancer of FIG.4.

Referring now to FIG. 7, there is illustrated a third embodiment of the feed enhancer of the present invention in which apaper tray700 has a heightened portion. The heightened portion comprises anelongated strip702 and an adjustment means for adjusting the height of theelongated strip702 above the top surface of the paper tray.

Referring now to FIGS. 8A,8B,9A, and9B, the adjustment means preferably comprises ashaft704 rotatably disposed in thepaper tray700 through

openings

706,708. Theshaft704 is retained in the

openings

706,708 at a first end with aknob710, preferably press fit onto theshaft704, and at a second end with a retainingring712. Acam714 is disposed on theshaft704 which has anouter surface716 which varies in distance from a central axis A—A of theshaft704. A portion of theouter surface716ais in contact with theelongated strip702 through opening718a. Theknob710 is preferably accessible from a front of thepaper tray700 such that a user can easily access theknob710 and rotate it, thus rotating thecam714 about theshaft704.

Retaining means retains theelongated strip702 along a path B—B perpendicular to thetop surface700aof thepaper tray700. Preferably the retaining means comprises at least twoshafts720 perpendicular to thetop surface700aof the paper tray700 (in other words, parallel to the movement of theelongated strip702 along axis B—B). Theshafts720 have afirst end720aslidingly disposed in thetop surface700aof thepaper tray700 and asecond end720bdisposed on theelongated strip702. Preferably, thesecond end720bof theshafts720 are press fit or tack welded into corresponding openings in theelongated strip702 and the first ends720aslide within corresponding holes on thetop surface700 of thepaper tray700. The first ends720aalso have alip720cfor preventing the first ends720afrom coming free from their corresponding holes. Biasing means, such as acompression spring722, are disposed around eachshaft720 for biasing theelongated strip702 toward thetop surface700aof thepaper tray700. The compression springs722 are also disposed between thetop surface700aof thepaper tray700 and thelip720cat the first ends720aof theshafts720.

Referring now to FIG. 10, the third embodiment of the feed enhancer of the present invention also preferably includes a locking means for locking theelongated strip702 at a predetermined height above thetop surface700aof thepaper tray700. The locking means preferably comprises aball detent800 disposed on thepaper tray700. Theball detent800 generally has a threaded body which mates with a corresponding threaded hole in thepaper tray700. Theball detent800 also has aball802 retained therein and biased towards theshaft704 by a biasing means, such as acompression spring804. A plurality ofdetents806, which are preferably conical shaped cavities, are disposed around the circumference of theshaft704.

The detents can be disposed on theshaft704 itself or alternatively, on adisk808 retained on theshaft704, preferably with a set screw or by press fitting. Theball802 engages acorresponding detent806aand is retained therein by the biasing force of thespring804 thereby locking theelongated strip702 at a height above thetop surface700aof thepaper tray700 corresponding to the circumferential location of the engageddetent806aon theshaft704.

It can be appreciated that as theknob710,shaft704, andcam714 attached thereto are rotated towardsdetent806bthe weight of theelongated strip702 and the biasing force ofsprings722 will bring theelongated strip702 into contact with theouter surface716 of thecam714. Theelongated strip702 is at its lowest height with respect to thetop surface700aof thepaper tray700 when the portion of thecam716bfaces theelongated strip702, as shown in FIGS. 8B and 9B. In this position,portion716aof thecam714 will retreat intoopening718b. Preferably, thepaper tray700 includes arecess700b, so that theelongated strip702 is flush with thetop surface700aofpaper tray700.

Obviously, the height of theelongated strip702 above thetop surface700aof thepaper tray700 is variable depending upon theparticular detent806 engaged with theball802. The incremental amount that the height can be adjusted is dependent upon the number ofdetents806 disposed about the circumference of theshaft704, or alternatively, thedisk808.

In operation, the rotation ofknob710 results in the height of theelongated strip702 above thetop surface700aof thepaper tray700 to increase or decrease depending on the distance from the central axis A—A of theshaft704 to the portion of theouter surface716 in contact with theelongated strip702.

The various embodiments of the feed enhancer of the present invention are illustrated as being in close proximity to thepick roller104. However, it should be apparent to those skilled in the art that the feed enhancers can be placed at various points along the length of the paper to be fed into the printer without departing from the scope or spirit of the present invention.

From the foregoing description, it can be appreciated by someone skilled in the art that the adjustment means can be utilized to offset varying degrees of height and unevenness in paper stacks. If the unevenness of the paper stack is severe, the height of the elongated strip can be increased as described. Alternatively, if the unevenness of the paper stack is minor, the height of the elongated strip can be decreased. The simplicity, inexpensiveness, and ease of retrofitting existing printers with the feed enhancer embodiments of the present invention, particularly the first embodiment illustrated in FIG. 4, can also be appreciated by an artisan skilled in the art.

While there has been shown and described what is considered to be preferred embodiments of the invention, it will, of course, be understood that various modifications and changes in form or detail could readily be made without departing from the spirit of the invention. It is therefore intended that the invention be not limited to the exact forms described and illustrated, but should be constructed to cover all modifications that may fall within the scope of the appended claims.

Claims

I claim:

1. A feed enhancer for eliminating an unevenness in height from a paper stack to be printed by a printer, the printer having a paper feeder including a paper tray for storage of the paper stack on a top surface thereof and for feeding individual paper from the paper stack into the printer for subsequent printing, the feed enhancer comprising;

an elongated strip disposed at the top surface of the paper tray and positioned perpendicular to a direction in which the individual paper is fed into the printer such that the feed enhancer evens out the unevenness in height of the paper stack in an area of the paper stack that is to be fed into the printer; and

mounting means for mounting the elongated strip to the top surface of the paper tray wherein the top surface of the paper tray is ferric and the mounting means is a magnetic strip fastened to the elongated strip whereby the elongated strip is mounted to the top surface of the paper tray by a magnetic attraction between the magnetic strip attached thereto and the top surface of the paper tray.

2. The feed enhancer according to claim1, wherein the elongated strip has a length substantially equal to the width of the paper in the direction perpendicular to which the individual paper is fed into the printer.

3. The feed enhancer according to claim1, further comprising a mounting means for mounting the elongated strip to the top surface of the paper tray.

4. The feed enhancer according to claim1, wherein the magnetic strip is fastened to the elongated strip with an adhesive.

5. A printer tray for eliminating an unevenness in height from a paper stack to be printed by a printer, the printer having a paper feeder including the paper tray for storage of the paper stack on a top surface thereof and for feeding individual paper from the paper stack into the printer for subsequent printing, the printer tray comprising;

a feed enhancer having a heightened portion disposed at the top surface of the paper tray and positioned perpendicular to a direction in which the individual paper is fed into the printer such that the feed enhancer evens out the unevenness in height of the paper stack in an area of the paper stack that is to be fed into the printer, wherein the heightened portion comprises an elongated strip and the elongated strip has a width substantially equal to the width of the paper in the perpendicular direction in which the individual paper is fed into the printer; and

mounting means for mounting the elongated strip to the top surface of the paper tray, wherein the top surface of the paper tray is ferric and the mounting means is a magnetic strip fastened to the elongated strip whereby the elongated strip is mounted to the top surface of the paper tray by a magnetic attraction between the magnetic strip attached thereto and the top surface of the paper tray.

6. The printer tray according to claim5, wherein the magnetic strip is fastened to the elongated strip with an adhesive.

7. A printer for eliminating an unevenness in height from a paper stack to be printed, the printer having a paper feeder including a paper tray for storage of the paper stack on a top surface thereof and for feeding individual paper from the paper stack into the printer for subsequent printing, the printer comprising;

a feed enhancer having a heightened portion disposed at the top surface of the paper tray and positioned perpendicular to a direction in which the individual paper is fed into the printer such that the feed enhancer evens out the unevenness in height of the paper stack in an area of the paper stack that is to be fed into the printer, wherein the heightened portion comprises an elongated strip; and

8. The printer according to claim7, wherein the elongated strip has a width substantially equal to the width of the paper in the perpendicular direction in which the individual paper is fed into the printer.

9. The printer according to claim7, wherein the magnetic strip is fastened to the elongated strip with an adhesive.

10. A printer tray for eliminating an unevenness in height from a paper stack to be printed by a printer, the printer having a paper feeder including the paper tray for storage of the paper stack on a top surface thereof and for feeding individual paper from the paper stack into the printer for subsequent printing, the printer tray comprising a feed enhancer having a heightened portion disposed at the top surface of the paper tray and positioned perpendicular to a direction in which the individual paper is fed into the printer such that the feed enhancer evens out the unevenness in height of the paper stack in an area of the paper stack that is to be fed into the printer, wherein the heightened portion comprises a stepped portion integral in one piece with the top surface of the paper tray.

11. The printer tray according to claim10, wherein the stepped portion has a width substantially equal to the width of the paper in the perpendicular direction in which the individual paper is fed into the printer.

12. A printer tray for eliminating an unevenness in height from a paper stack to be printed by a printer, the printer having a paper feeder including the paper tray for storage of the paper stack on a top surface thereof and for feeding individual paper from the paper stack into the printer for subsequent printing, the printer tray comprising a feed enhancer having a heightened portion disposed at the top surface of the paper tray and positioned perpendicular to a direction in which the individual paper is fed into the printer such that the feed enhancer evens out the unevenness in height of the paper stack in an area of the paper stack that is to be fed into the printer, wherein the heightened portion comprises an elongated strip and an adjustment means for adjusting the height of the elongated strip above the top surface of the paper tray, the adjustment means comprising:

a shaft rotatably disposed in the paper tray;

a cam disposed on the shaft, the cam having an outer surface which varies in distance from a central axis of the shaft, a portion of the outer surface being in contact with the elongated strip;

retaining means for retaining the elongated strip along a path perpendicular to the top surface of the paper tray; and

a knob rotatably engaged with the shaft and accessible from a front of the paper tray for rotating the cam about the shaft, the rotation of which resulting in the height of the elongated strip above the top surface of the paper tray to increase or decrease depending on the distance from the central axis of the shaft to the portion of the outer surface in contact with the elongated strip.

13. The printer tray according to claim12, wherein the retaining means comprises:

at least two shafts perpendicular to the elongated strip, the shafts having a first end fixed on the elongated strip and a second end slidingly disposed on the top surface of the paper tray; and

biasing means for biasing the elongated strip toward the top surface of the paper tray.

14. The printer tray according to claim13, wherein the biasing means comprises a compression spring disposed around each shaft between the top surface of the paper tray and a lip at the second end of the shafts.

15. The printer tray according to claim12, further comprising a locking means for locking the elongated strip at a predetermined height above the top surface of the paper tray.

16. The printer tray according to claim15, wherein the locking means comprises:

a ball detent disposed on the paper tray, the ball detent having a ball retained therein, the ball being biased towards the shaft by a biasing means; and a plurality of detents disposed around the circumference of the shaft, whereby the ball engages a corresponding detent and is retained therein by the biasing force of the biasing means thereby locking the elongated strip at a height above the top surface of the paper tray corresponding to the circumferential location of the engaged detent on the shaft.

17. A printer for eliminating an unevenness in height from a paper stack to be printed, the printer having a paper feeder including a paper tray for storage of the paper stack on a top surface thereof and for feeding individual paper from the paper stack into the printer for subsequent printing, the printer comprising a feed enhancer having a heightened portion disposed at the top surface of the paper tray and positioned perpendicular to a direction in which the individual paper is fed into the printer such that the feed enhancer evens out the unevenness in height of the paper stack in an area of the paper stack that is to be fed into the printer, wherein the heightened portion comprises a stepped portion integral in one piece with the top surface of the paper tray.

18. The printer according to claim17, wherein the stepped portion has a width substantially equal to the width of the paper in the perpendicular direction in which the individual paper is fed into the printer.

19. A printer for eliminating an unevenness in height from a paper stack to be printed, the printer having a paper feeder including a paper tray for storage of the paper stack on a top surface thereof and for feeding individual paper from the paper stack into the printer for subsequent printing, the printer comprising a feed enhancer having a heightened portion disposed at the top surface of the paper tray and positioned perpendicular to a direction in which the individual paper is fed into the printer such that the feed enhancer evens out the unevenness in height of the paper stack in an area of the paper stack that is to be fed into the printer, wherein the heightened portion comprises an elongated strip and an adjustment means for adjusting the height of the elongated strip above and parallel to the top surface of the paper tray.

20. The printer according to claim19, wherein the adjustment means comprises:

a shaft rotatably disposed in the paper tray;

21. The printer according to claim20, wherein the retaining means comprises:

22. The printer according to claim21, wherein the biasing means comprises a compression spring disposed around each shaft between the top surface of the paper tray and a lip at the second end of the shafts.

23. The printer according to claim20, further comprising a locking means for locking the elongated strip at a predetermined height above the top surface of the paper tray.

24. The printer according to claim23, wherein the locking means comprises:

a ball detent disposed on the paper tray, the ball detent having a ball retained therein, the ball being biased towards the shaft by a biasing means; and

a plurality of detents disposed around the circumference of the shaft, whereby the ball engages a corresponding detent and is retained therein by the biasing force of the biasing means thereby locking the elongated strip at a height above the top surface of the paper tray corresponding to the circumferential location of the engaged detent on the shaft.